This invention relates to a shutter blade operating device for a camera, and more particularly, to a shutter blade operating device of the type wherein exposure motion is performed by two pairs of shutter blades running across a shutter aperture in sequence.
Recently, as reduction in size of portable cameras becomes more popular, the demand for reduced sized shutters is increasing, and particularly, reduction of size of the shutter blade operating device and its control device is being eagerly sought.
In reducing the size of a shutter, it is an important condition to reduce the total dimension of the shutter without changing the diameter of the shutter aperture and without deteriorating the performance of the shutter.
In general, the motion of a shutter blade occurs in three ranges; a first range where the shutter blade starts moving and appears in the aperture, a second range where the shutter blade passes across the aperture and a third range where the shutter blade disappears out of the aperture and finishes its motion. While the shutter blade moves across the second range, a photosensitive film is exposed to light. The first range is a preliminary range provided for stabilizing the movement of the shutter blade. The third range is a final range provided to prevent the shutter blade from rebounding back into the aperture.
Although the second range is essential for the shutter performance and may not change because the size of the aperture is fixed due to functional reasons, the first and the third ranges may be reduced.
In most cameras of today, the film winding and shutter cocking strokes are performed simultaneously in one action and this requires that the stroke of film winding and that of shutter cocking be identical, however, this condition requires a complicated mechanism. In general, such cameras are designed based on priority of the film winding stroke and providing an allowance for the stroke for shutter cocking. Therefore, it is necessary to construct the shutter so as not to be damaged even if the shutter is cocked more than the required stroke.
This condition will not be a problem for the type shutter in which exposure is performed by the reciprocating motion of a pair of blades; however, for a variable-slit shutter in which exposure is performed by the motion of two pairs of shutter blades, there is the possibility that the shutter blades will project out of the confines of their motion.
An object of this invention is to provide a shutter blade operating device of a reduced size which is achieved by narrowing the first and the second ranges while providing means for ensuring that the shutter blades do not project out of the confines of their motion. The essential feature of the shutter blade operating device of this invention is that two pairs of shutter blade sets and shutter blade operating members are interconnected through a pair of springs so that both shutter blade operating members are cocked at the same time during the shutter cocking motion and each shutter blade set is cocked by its corresponding shutter blade operating member through the spring provided between them.